Homework Help:
Electric Field of a Hollow Cylidrical Conductor

Consider a hollow cylindrical conductor in vacuum with its axis aligned with
the z-axis, and with a positive surface charge density σ. The direction of the
electric field is radial and its magnitude E is only a function of the distance r
from the z-axis, E = E(r).

Use Gauss' law to obtain the magnitude of the electric field at r < R and
at r ≥ R, where R is the radius of the conductor.

I don't know whether I have got my brain stuck in a rut but I can't for the life of me solve this. Any and all help will be greatly appreciated :D

Use the cylinder with surface area of 2*PI*r*l
Do the calculation using the information they have given you, and it should all come out nicely. (Even though the conductor is infinite, it doesn't go bad).